Containers have become the go-to choice for many development teams as they’re fast and lightweight. But, as always, with benefits there is also risk. Last year, nearly half (46%) of organizations surveyed by Red Hat experienced revenue or customer loss due to container or Kubernetes security incidents. Container security is now essential to keep applications and infrastructure safe.
Understanding Container Security
Container security is about protecting containerized applications, the environments they run in, and everything that interacts with them. And, really, it is “everything,” considering that containers affect code, pipelines, the orchestration layer, runtime environments, and supply chains.
As more organizations use containerized applications, the attack surface expands, making it critical to protect workloads from cyber threats and maintain compliance.
Container security covers:
-
Images you build.
-
Registries that store them.
-
The orchestration platform (usually Kubernetes).
-
Container runtime environment.
-
Supply chain that feeds your production deployments.
Why Containers Need Different Security
Traditional security models don’t always work for container technologies, because containers are created, deployed, and destroyed in short-lived cycles. The old idea of scanning a static server or reviewing a fixed environment doesn’t apply anymore.
Teams are no longer only safeguarding a single monolithic application, but are now responsible for dozens (or hundreds) of small components that spin up and down automatically.
Security has to be more distributed and integrated into the software development lifecycle.
Container Security Risks and Threats
Containers make deployment easier, but they can also lead to a whole set of risks that didn’t exist before.
Vulnerable Images
Container images are reused across teams and environments, so any weakness is multiplied at scale.
Vulnerability scanners are helpful in catching known issues in container images, but risk also comes from oversized images, outdated base layers, and unnecessary components. The more that’s included, the harder it is to see what’s running in production.
Public base images that are used without review can spread risk across pipelines. If an image isn’t built carefully, every deployment that depends on it inherits the same flaws.
Misconfigurations
Teams can have a clean image with no known CVEs, but still expose the environment if the container is not configured properly. Misconfigurations are still one of the top causes of security incidents because they’re easy to overlook and often happen accidentally.
Running a container as root, exposing unnecessary ports, or over-granting permissions can turn into a critical vulnerability.
Also, misconfigurations can result in failing compliance requirements and regulatory standards, putting organizations at risk of non-compliance fines. Teams should always follow container security best practices.
Supply Chain Risks
The risk doesn’t stop at what’s inside the image, but also extends to how images are built, versioned, and promoted through pipelines.
As containers have different layers and dependencies from various sources, each step in that supply chain introduces potential security issues.
Software Bills of Materials (SBOMs) are becoming a central part of security, especially with containers. An SBOM provides a clear inventory of all components in an image, including libraries, frameworks, and packages, along with their versions.
Without this kind of visibility, organizations can’t reliably track vulnerabilities or understand where exposure exists.
Secrets in the Wrong Place
Hard-coding secrets in Dockerfiles, environment variables, or config maps is still surprisingly common. Attackers don’t need to break in if your credentials are waiting for them in plaintext.
According to the IBM Cost of a Data Breach Report, breaches caused by compromised credentials took the longest to identify and contain.
Runtime Threats
Clean, well-configured containers can still behave in unexpected ways during runtime. Malware, unauthorized system calls, and lateral movement attempts all come under runtime risks.
In short, you can’t assume containers are safe just because they’re isolated. They still need protection built around them.
Challenges in Container Security
As powerful as containers are, teams often struggle with similar issues:
Permission Overload
It’s easy to “just give it the permissions it needs to work” without fully realizing how broad those permissions are.
Unpatched Images
Container images preserve every dependency exactly as it was at build time. A vulnerability that’s there when you built the image will remain until you specifically rebuild and redeploy.
Orchestrator Complexity
As clusters grow, the complexity grows with them, and security controls don’t always scale as fast.
Skills Gaps
Many developers understand containers well but haven’t been trained to secure them, leaving a gap between intention and execution.
These challenges are solvable with a combination of automated tooling, security policies, and practical team security training.
For container security to be effective, follow the best practices below and use container security solutions, such as vulnerability scanners, runtime security tools, and network security, to enhance the overall security posture.
Building a Container Security Strategy
A strong container security strategy doesn’t need to be overly complicated, but focus on the right areas.
1. Secure Image Creation
Securing containers starts before the container even exists. A typical image builds on top of a base image, often pulled from a public registry, and that’s where many issues can be prevented early.
To secure image creation:
-
Start with trusted, official base images.
-
Keep images lean by removing anything that isn’t needed.
-
Automate vulnerability scanning during CI.
-
Lock down what dependencies can be used in builds.
This is also a great place to reinforce developer habits. A clean Dockerfile goes a long way in reducing your attack surface.
2. Image Registry Security
Container registries manage container images throughout your organization. Without proper security controls, unauthorized access to your registry allows attackers to replace legitimate images with malicious versions.
Your container registry is the single point of control between development and production, so if the registry is compromised, everything downstream is at risk.
Registry best practices include:
-
Using private registries whenever possible.
-
Enforcing access controls and multi-factor authentication.
-
Scanning stored images regularly, not just at build time.
-
Using image signing to verify integrity before deployment.
If the registry is trustworthy, deployments are much easier to secure.
3. Hardening Orchestrators
Orchestrators, such as Kubernetes, manage every aspect of your containerized workloads, and that level of control comes with hundreds of configuration options that need proper security settings.
Some foundational protections include:
-
Applying Pod Security Standards.
-
Limiting network communication between pods.
-
Blocking privileged containers.
-
Using admission controllers to enforce rules automatically.
-
Setting CPU and memory limits to prevent resource abuse.
It’s a good idea to start with the built-in security features of Kubernetes and other orchestrators, such as role-based access control (RBAC) and secrets management, to enhance container security.
4. Secrets Management
Containers should never store sensitive information directly, so secrets shouldn’t live in images, Dockerfiles, or plaintext environment variables.
Better approaches include:
-
Using managed secrets services (AWS Secrets Manager, GCP Secret Manager, Vault, etc.)
-
Rotating credentials regularly.
-
Encrypting everything at rest and in transit.
-
Not passing secrets through logs or plain environment variables.
Secrets management is one of the fastest ways to improve container security, but it’s often overlooked.
5. Continuous Monitoring and Runtime Protection
A secure build is only the beginning, because visibility into how containers behave in production is also needed.
Runtime monitoring helps you detect:
-
Unusual network traffic.
-
Unexpected filesystem changes.
-
Suspicious commands.
-
Containers spawning processes they shouldn’t.
-
Lateral movement attempts inside the cluster.
Containers may be temporary, but the vulnerabilities they introduce aren’t. Runtime monitoring detects threats as they emerge, and, in general, security monitoring helps maintain visibility into container activities.
Best Practices for Securing Containers
While there are plenty of tools that can identify vulnerabilities in images or find misconfigurations, container security also relies on the people who deploy and maintain these systems, including developers, DevSecOps, and security teams.
If developers don’t understand why certain practices are important, they’ll continue to deploy workloads that look fine on a dashboard but aren’t really safe.
Bringing it all together, here are some practical ways to keep containers secure:
Development Phase:
-
Shift security left into development workflows.
-
Integrate vulnerability scanning into the CI/CD pipeline.
-
Use policy-as-code tools to apply rules consistently.
-
Implement automated security testing.
Build and Deploy Phase:
-
Regularly update and rebuild images.
-
Sign images and verify signatures before deployment.
-
Track and verify the source of images.
-
Treat containers as immutable, rebuild and redeploy rather than patching running containers.
Runtime Phase:
-
Apply the principle of least privilege everywhere.
-
Log events at the cluster, node, and container levels.
-
Monitor for runtime anomalies.
-
Implement network segmentation.
Continuous Improvement:
-
Automate what you can, as consistency is key.
-
Conduct regular security audits.
-
Keep team skills up to date with hands-on training.
-
Review and update security policies quarterly.
Security becomes much easier when it’s part of the build and deployment process.
How SecureFlag Helps Organizations Improve Container Security
Container security is a hands-on discipline, and that’s precisely where SecureFlag helps. Through real cloud environments, including AWS, Azure, and GCP, developers learn how to:
-
Find insecure Dockerfiles.
-
Fix misconfigured containers.
-
Harden Kubernetes deployments.
-
Secure containerized pipelines.
-
Reduce misconfigurations that often lead to vulnerabilities.
The learning experience goes beyond theory. Teams work directly with containers, cloud services, and Kubernetes clusters, giving them the confidence to build and run secure applications.
SecureFlag helps organizations raise their overall application security posture by giving developers the practical skills they need to secure containerized systems.
